The present invention relates to a self-diagnosis apparatus for vehicle which stores and holds diagnosis data necessary for analysis of abnormality of equipment mounted on the vehicle.
Recently, the electronization of a vehicle is remarkable so that equipment mounted on various parts of a vehicle inclusive of an engine are organically coupled with each other by a control computer to perform complicated operations.
In many cases, even if the abnormality of the operation of a certain single equipment is detected, a true cause for abnormality is not ascertained for a relation with the other equipment unless data indicative of a vehicle condition at that time (or diagnosis data) is collected in a wide range. Also, a temporary abnormality in operation may be followed by a natural recovery from the abnormality. In many cases, this is a precursory phenomenon of a perfect failure. However, it is very difficult to find out a cause for temporary abnormality by a check after the alighting from the vehicle.
JP-A-62-142849 and JP-A-63-159623 have proposed a self-diagnosis apparatus in which diagnosis data of various parts of a vehicle is stored into a in an updated form at every fixed period and the updating of the contents of the memory after the detection of an abnormality of an equipment mounted on the vehicle is inhibited (or frozen), thereby making it possible to accurately grasp a cause for the abnormality after the alighting from the vehicle. The memory holds its stored contents even at the time of cut-off of an ignition switch.
Also, JP-A-3-92564 has proposed an apparatus in which a control program as well as diagnosis data as mentioned above are stored in a memory, thereby making an attempt to grasp a cause for abnormality more accurately.